Jump to content

Help--Need a Harman Kardon 430 tech.


JohnW

Recommended Posts

Should I just go through every board and check continuity from every solder point to every solder point? 

On 2/14/2022 at 7:35 PM, captainbeefheart said:

 

200k should be good.

 

As for capacitors when you pull the old ones off measure the lead spacing on the board and also the casing diameter. Caps have gotten smaller and the 2200uF 35v that I linked below has a 7.5mm lead spacing. Case diameter is most likely not going to be an issue since caps have become smaller but using too small lead spacing makes the capacitor sit weird on the board so you should try and get a capacitor with the correct lead spacing. Digikey is nice because you can use the lead spacing as a search criteria along with voltage rating and capacitance and view the results.

 

https://www.digikey.com/en/products/detail/rubycon/35ZLH2200MEFC16X25/3564493

 

It looks like the lead spacing on the currently-installed 4700uF 35v filter capacitors is about an inch...can't seem to find a matching pair. Any guidance?

Link to comment
Share on other sites

1 hour ago, JohnW said:

It looks like the lead spacing on the currently-installed 4700uF 35v filter capacitors is about an inch...can't seem to find a matching pair. Any guidance?

 

Those are the main filter caps for the +/- supply on board C.  Are you positive you measured an inch? That sounds too large even for older caps of this era. I would think more closer to 1/2 an inch lead spacing. You may have to get radial through holes type and not snap in, 10mm is about as large a lead spacing as you will get so just bend the leads flat along the bottom of the cap and then 90° bend down where the through holes are on the board. Use something to adhere the cap to the board if you can't find exact lead spacing.

 

https://www.digikey.com/en/products/detail/nichicon/UVR1V472MRD6/588830

Link to comment
Share on other sites

On 2/14/2022 at 1:29 PM, captainbeefheart said:

 

The filter cap (C4) is on the rectifier board and is connected via a trace. It's painfully clear that we still have a major problem so the rectifier board should be removed and fully tested. We just need to find if the fault is on the rectifier board or after it on the load side where LP53 connects.

 

 

 

On 2/14/2022 at 1:04 PM, babadono said:

The ones going to the loads not the inputs. So if I am decoding the manual properly/sufficiently I would say the red,orange and possibly the white/orange. Double check me please @captainbeefheart. It is possible that the filter caps are dried out old electrolytics and are not performing as they should. Also there is a member here who fixes Klipsch subwoofer amp boards and he swears that glue sometimes becomes conductive.

Ok, so you're suggesting I remove the Red, Orange, and White/Orange wires from Rectifier A and then try powering it up again with the R9 resistor in place? 

Any idea how the board is grounded? 

Should I learn how to build a Dim Bulb Tester before I do this?

Link to comment
Share on other sites

13 minutes ago, JohnW said:

Or should I just pull the rectifier A and B boards, unsolder every diode, capacitor, resistor and transistor, and test them individually?

 

R9 only passes current for rectifier boards A and B. Board C shouldn't be of concern right now until you get the amp up and running.

 

If I was tasked at repairing this unit I would remove rectifier boards A and B and put them on the bench. I would use my variac to input the desired AC voltage to LP55 and LP56 on board A. Note you have to connect board A to board B with a wire between L54 and LP 63. I would then put a resistive load at the output of both boards A and B, maybe 20mA or so should be fine. Then I would power it up while monitoring AC current draw and quickly take voltage readings around Q1 and Q2. This should tell me which board is messed up and possibly which part.

 

If I didn't have the means to do that I would probably remove boards A and B and yes remove transistors, diodes, and capacitors and test them out of circuit.

Link to comment
Share on other sites

3 minutes ago, captainbeefheart said:

 

R9 only passes current for rectifier boards A and B. Board C shouldn't be of concern right now until you get the amp up and running.

 

If I was tasked at repairing this unit I would remove rectifier boards A and B and put them on the bench. I would use my variac to input the desired AC voltage to LP55 and LP56 on board A. Note you have to connect board A to board B with a wire between L54 and LP 63. I would then put a resistive load at the output of both boards A and B, maybe 20mA or so should be fine. Then I would power it up while monitoring AC current draw and quickly take voltage readings around Q1 and Q2. This should tell me which board is messed up and possibly which part.

 

If I didn't have the means to do that I would probably remove boards A and B and yes remove transistors, diodes, and capacitors and test them out of circuit.

I was afraid you'd say that. :D

New caps are on the way. I should likely just buy new transistors and diodes as well, since I can test resistors in the board. 

I almost want to pay someone locally to dig into this, because I'm in way over my head. 
But I'm stubborn af

 

  • Like 1
Link to comment
Share on other sites

4 hours ago, JohnW said:

Ok, so you're suggesting I remove the Red, Orange, and White/Orange wires from Rectifier A and then try powering it up again with the R9 resistor in place? Yes

Any idea how the board is grounded? 

Both A and B boards have a metal eyelet attached to them that then screws to the chassis correct? That is ground I'm thinking.

  • Like 1
Link to comment
Share on other sites

21 minutes ago, captainbeefheart said:

Intermittent issues are enough to drive anyone crazy sometimes. Let's hope the problem is gone for good now but from experience it most likely will come back.

Undoubtedly. But this little victory makes further battles worthwhile. Thing sounds truly amazing. I think I'll keep it, and do what I can to keep it alive, for now. 

  • Like 1
Link to comment
Share on other sites

11 minutes ago, captainbeefheart said:

Looks like the boards have a ground trace where I circled in red where the boards mount to the chassis. Possibly check them as well and make sure they are good.

 

 

grounds.png

That's what I loosened and tightened. 

Thanks again for all your patience and help. 

(not that we're done here, of course :) )

Link to comment
Share on other sites

9 minutes ago, JohnW said:

That's what I loosened and tightened. 

Thanks again for all your patience and help. 

(not that we're done here, of course :) )

 

Double check because there might also be dedicated grounds going to the other boards via a wire. I circled them in red here. Often the ground that you tightened where the board mounts to chassis is a redundant extra ground.

 

 

grounds2.png

  • Like 2
Link to comment
Share on other sites

41 minutes ago, JohnW said:

That's what I loosened and tightened. 

Roger...you tightened it to the chassis. But how is attached to the board itself? If soldered it can crack, if just a mechanical connection it can oxidize. Details...details..that's where the devil hides....

  • Like 1
Link to comment
Share on other sites

2 minutes ago, babadono said:

Roger...you tightened it to the chassis. But how is attached to the board itself? If soldered it can crack, if just a mechanical connection it can oxidize. Details...details..that's where the devil hides....

It's screwed into the board and into the chassis. I loosened and re-tightened. 

But perhaps the whole issue was shitty resistors? 

Link to comment
Share on other sites

But maybe that isn't it. I tested across it, both before I soldered it in and after, and those big voltages (5-6) at startup weren't there anymore. 

I had replaced the filter cap fuses, but the previous ones were the correct ones, and still conducting...

Maybe it was the ground. 

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...